1. FIELD OF THE INVENTION
The present invention relates to an integrated circuit package.
2. DESCRIPTION OF RELATED ART
Integrated circuits are typically assembled into a package that is mounted to a printed circuit board. There are a number of different types of integrated circuit packages including quad flat pack (QFP), pin grid array (PGA) and ball grid array (BGA) packages. BGA packages include a number of solder balls that are soldered to corresponding solder pads located on the bottom surface of a substrate. The solder balls are reflowed to attach the substrate to a printed circuit board.
An integrated circuit is mounted to a top surface of the substrate. The integrated circuit is coupled to bond pads located on the top surface of the substrate. The bond pads are connected to the solder pads by a number of vias and routing traces formed within the substrate. The integrated circuit is typically enclosed by a protective molded plastic material. The molding process increases the cost of the package. It would be desirable to eliminate the plastic housing while still covering the integrated circuit.
The heat generated by the integrated circuit conducts into the printed circuit board through the vias, the routing traces and the solder balls. The vias and routing traces have a relatively high thermal impedance. The high thermal impedance creates an undesirable temperature differential between the circuit board and the integrated circuit. The high temperature differential may create junction temperatures which exceed the recommended operating limits of the integrated circuit. Some packages incorporate heat slugs into the plastic housing to remove heat from the top surface of the integrated circuit die. Heat slugs add to the complexity and cost of mass producing the package. It would be desirable to provide an integrated circuit package that provides an alternate thermal path for heat to flow from the substrate to reduce the overall thermal impedance of the package.